Optical networks are used to deliver voice, data and video services to multiple network subscribers using one or more optical fibers. The optical networks deployed to deliver the voice, data and video services may be either passive or active. In a passive optical network (PON), for example, passive optical splitters and combiners enable multiple subscribers to share the same optical fiber. Thus, the PON functions as a point-to-multipoint optical network. A PON may conform to any of a variety of PON standards, such as broadband PON (BPON) (ITU G983), gigabit-capable PON (GPON) (ITU G984), or gigabit-capable Ethernet PON (GEPON or EPON) (IEEE 802.3). In an active optical network, some sort of electrically powered equipment, such as a switch, router, or multiplexer, distributes the signal to the subscriber to which the signal is destined. Thus, an active optical network, such as an active Ethernet (AE) optical network (IEEE 802.3ah), may operate as a point-to-point network.
When optical fiber extends to a premise where one or more subscriber devices are located, the service is commonly referred to as Fiber to the Premises (FTTP) or Fiber to the Home (FTTH). In FTTP/FTTH services, a network interface device, such as an optical network unit (ONU), terminates an optical fiber of the optical network, and delivers the signals on the optical fiber to subscriber devices to provide FTTP services. Subscriber devices may include, for example, televisions, set-top boxes, telephones, computers, or other network client devices. The ONU also receives signals from subscriber devices, and transmits the signals upstream via the optical network. In this manner, the ONU can support a wide variety of services, including voice, video and data services, over the optical network.